1. Field of the Invention
The present invention relates to an anisotropic conductive material body, a display apparatus, a method for producing the display apparatus, and a conductive member. More specifically, the present invention relates to an anisotropic conductive material body usable for electrically connecting electronic components, a display apparatus including a driving circuit mounted using such an anisotropic conductive material body, a method for producing the display apparatus, and a conductive member suitable for the anisotropic conductive material body.
2. Description of the Related Art
In a display apparatus such as, for example, a liquid crystal display apparatus, a driving signal which is output from a driving circuit is input to a display panel. In a general display apparatus, a display panel including a plurality of pixels is provided with a plurality of panel connectors at a fine pitch. The driving circuit includes a plurality of driving circuit connectors. The plurality of driving circuit connectors respectively correspond to, and connect with, the panel connectors.
The driving circuit is mounted on the display panel by TAB (Tape Automated Bonding), COG (Chip On Glass) or the like. For such a manner of mounting, an anisotropic conductive layer is used.
Japanese Laid-Open Publication No. 6-59268 discloses a structure for mounting a driving circuit on a display panel using an anisotropic conductive layer.
FIG. 4 is a schematic cross-sectional view of a mounting structure disclosed in Japanese Laid-Open Publication No. 6-59268.
The mounting structure shown in FIG. 4 is provided on a peripheral portion of a liquid crystal display panel 30 as more specifically described below. On the peripheral portion, a plurality of panel connectors 31 are provided at a fine pitch. The plurality of panel connectors 31 receive, for example, a driving signal for driving the liquid crystal display panel 30. Also on the peripheral portion, a driving circuit 33 for supplying a driving signal or the like is mounted by an anisotropic conductive layer 34. The driving circuit 33 is a source COF (Chip on Film) section, a gate COF section, or the like.
The plurality of panel connectors 31 are provided so as to project from a surface of the liquid crystal display panel 30 toward the driving circuit 33. A plurality of driving circuit connectors 33a are provided so as to project from a surface of the driving circuit 33 toward the liquid crystal display panel 30. The plurality of driving circuit connectors 33a are located to face the corresponding panel connectors 31, respectively.
An anisotropic conductive layer 34 includes a synthetic resin 34a, a plurality of conductive particles 34b dispersed in the synthetic resin 34a, and a plurality of insulating particles 34c dispersed in the synthetic resin 34a. The plurality of conductive particles 34b contain metal such as nickel or the like. The synthetic resin 34a has an adhering property and acts as an adhesive.
The driving circuit 33 is bonded to the peripheral portion of the liquid crystal display panel 30 with the synthetic resin 34a. The plurality of driving circuit connectors 33a and the corresponding panel connectors 31 are electrically connected to each other with the conductive particles 34b, respectively. Accordingly, a driving signal which is output from the driving circuit 33 is input to the liquid crystal display panel 30 via the driving circuit connectors 33a, the conductive particles 34b, and the panel connectors 31.
The mounting structure shown in FIG. 4 is produced as follows.
The anisotropic conductive layer 34 is provided so as to cover the panel connectors 31 which are located on the peripheral portion of the liquid crystal display panel 30. The driving circuit 33 with the driving circuit connectors 33a is located on the anisotropic conductive layer 34. The driving circuit 33 is positioned with respect to the liquid crystal display panel 30 such that the driving circuit connectors 33a face the corresponding the panel connectors 31, respectively.
In this state, the driving circuit 33 is pressed on the anisotropic conductive layer 34, and the anisotropic conductive layer 34 is heated. When the anisotropic conductive layer 34 is heated, the synthetic resin 34a becomes a dissolved state, and the conductive particles 34b dispersed in the synthetic resin 34a flow into areas between the driving circuit connectors 33a and the corresponding panel connectors 31. The driving circuit connectors 33a and the corresponding panel connectors 31 are electrically connected to each other with the conductive particles 34b. Then, the synthetic resin 34a is cured, and thus the driving circuit 33 is mounted on the peripheral portion of the liquid crystal display panel 30.
Japanese Laid-Open Publication No. 5-29386 discloses a mounting structure using an anisotropic conductive layer.
FIG. 5 is a schematic cross-sectional view disclosed in Japanese Laid-Open Publication No. 5-29386.
In the mounting structure shown in FIG. 5, a plurality of panel connectors 41 are provided at a fine pitch on a peripheral portion of a liquid crystal display panel 40.
The plurality of panel connectors 41 are provided so as to project from a surface of the liquid crystal display panel 40 toward a driving circuit 43. A plurality of driving circuit connectors 43a are provided so as to project from a surface of the driving circuit 43 toward the liquid crystal display panel 40.
An anisotropic conductive layer 45 includes a synthetic resin 45a and a plurality of conductive particles 45b dispersed in the synthetic resin 45a. The synthetic resin 45a acts as an adhesive.
In the mounting structure shown in FIG. 5, the plurality of panel connectors 41 each have a recessed portion 41a. 
The depth of the recessed portion 41a is smaller than the particle diameter of the conductive particles 45b dispersed in the synthetic resin 45a. 
Owing to such a depth of the recessed portion 41a, the conductive particles 45b flowing in the recessed portion 41a are suppressed from flowing out from the recessed portion 41a. Therefore, a bottom surface of the recessed portion 41a and the corresponding driving circuit connector 43a are electrically connected to each other with certainty by the conductive particles 45b. 
In the mounting structure shown in FIG. 4, the panel connectors 31 project from the surface of the liquid crystal display panel 30 and the driving circuit connectors 33a project from a surface of the driving circuit 33. Therefore, the gap between the panel connectors 31 and the driving circuit connectors 33a is small. By contrast, the gap between an upper surface of a portion of the liquid crystal display panel 30 which does not have a panel connector 31 thereon, and a lower surface of a portion of the driving circuit 33 which does not have a driving circuit connector 33a thereon, is larger. Therefore, the anisotropic conductive layer 34 needs to be thick in order to mount the driving circuit 33 on the liquid crystal display panel 30. Production of such a thick anisotropic conductive layer 34 requires a larger amount of synthetic resin 34a, which increases the production cost.
In the mounting structure shown in FIG. 5, the panel connectors 41 project from the surface of the liquid crystal display panel 40 and the driving circuit connectors 43a project from the surface of the driving circuit 43. Therefore, the gap between the panel connectors 41 and the driving circuit connectors 43a is small. By contrast, the gap between an upper surface of a portion of the liquid crystal display panel 40 which does not have a panel connector 41 thereon, and a lower surface of a portion of the driving circuit 43 which does not have a driving circuit connector 43a thereon, is larger. Therefore, the anisotropic conductive layer 45 needs to be thick in order to mount the driving circuit 43 on the liquid crystal display panel 40. Production of such a thick anisotropic conductive layer 45 requires a larger amount of synthetic resin 45a, which increases the production cost.
In order to solve these problems, another mounting structure is proposed.
FIG. 6 is a cross-sectional view illustrating another conventional mounting structure.
In the mounting structure shown in FIG. 6, one continuous panel connector 51 is provided for one driving circuit 53, without being divided to correspond to a plurality of driving circuit connectors 53a. The panel connector 51 has a plurality of recessed portions 51a respectively facing the plurality of driving circuit connectors 53a. The depth of each recessed portion 51a is smaller than the particle diameter of conductive particles 55b of an anisotropic conductive layer 55.
On a bottom surface of each recessed portion 51a, a connector 51b is provided. The plurality of connectors 51b are provided at a fine pitch.
The conductive particles 55b are each in contact with, and thus electrically connect, the corresponding driving circuit connector 53a and the corresponding connector 51b. 
A driving signal which is output from the driving circuit 53 is input to a liquid crystal display panel 50 via the driving circuit connectors 53a, the conductive particles 55b, the connectors 51b, and the panel connectors 51.
In this mounting structure, the driving circuit connector 53a is electrically connected to the connector 51b with certainty by the conductive particles 55b flowing in the recessed portion 51a of the panel connector 51. The gap between the upper surface of a portion of the panel connector 51 which does not have a recessed portion 51a thereon, and the lower surface of a portion of the driving circuit 53 which does not have a driving circuit connector 53a thereon, is small. This allows the anisotropic conductive layer 55 used for mounting the driving circuit 53 to be thinner.
However, in the mounting structure shown in FIG. 6, each conductive particle 55b needs to have a large particle diameter such that the conductive particle 55b can contact both the driving circuit connector 53a and the connector 51b located on the bottom surface of the recessed portion 51a. For example, the conductive particle 55b needs to have a particle diameter of 10 μm or greater.
When the particle diameter of the conductive particle 55b is that large, the conductive particle 55b is compressed to be flatter in a gap between the upper surface of the panel connector 51 and the lower surface of a portion of the driving circuit 53 which does not have the driving circuit connector 53a. This may cause an undesirable result that adjacent conductive particles 55b contact, and to be conductive to, each other.
The driving circuit connectors 53a are provided at a fine pitch, like the recessed portions 51a of the panel connector 51. The pitch is usually about 100 μm. When the driving circuit connectors 53a are provided at such a fine pitch, the particle diameter of the conductive particles 55b of about 10 μm may cause the following undesirable result. When the conductive particles 55b are compressed to be flatter, adjacent conductive particles 55b become conductive to each other between two adjacent driving circuit connectors 53a and thus the adjacent driving circuit connectors 53a are short circuited.
The possibility that the above undesirable result occurs is low if the particle diameter of the conductive particles is about 3 to 5 μm. However, it cannot be guaranteed that such small conductive particles electrically connect the driving circuit connectors 53a and the connectors 51b on the bottom surfaces of the recessed portions 51a of the panel connector 51 to each other.